This invention relates to electrically conductive circuits made from metal powder compositions, as well as to methods for their manufacture.
Patterned metal articles, such as printed circuit boards, have many uses in the electronics industry. Printed circuits may be made by applying pressure with a heated die to metallic particles on an adhesive-coated substrate. Metal particles may also be mixed with a curable organic binder, and applied to a substrate using an adhesive layer, heat and pressure. Printed circuits may also be produced by embedding conductive granules mixed with an inorganic matrix material into a heat-softenable substrate. Silk screening methods may also be used to apply mixtures of organic materials and conductive particles to substrates, and compositions including metallo-organic decomposition compounds and metallic particles may also be silk screened on a substrate and heated to form a circuit pattern.
The adhesives and organic binders in these compositions are poor conductors of electricity, and, when mixed with metallic particles, reduce the overall conductivity of the resulting circuit pattern. The use of inorganic and metallo-organic compounds is limited to specific combinations of materials and particular substrates, and requires high processing temperatures.
In one aspect, the invention is a method for making an electrically conductive pattern, including: (a) depositing on a substrate a metal powder composition consisting essentially of at least one metal powder, wherein the substrate is selected from the group consisting of paper and materials that are at least about 10% compressible; and (b) densifying the composition to form a conductive pattern on the substrate.
In another aspect, the invention is an article with circuit elements including a conductive pattern on a substrate, wherein the conductive pattern consists essentially of at least one densified metal powder, and wherein the substrate is selected from the group consisting of paper and materials that are at least about 10% compressible.
The invention makes it possible to produce a suitably conductive pattern including circuit elements on paper and other compressible substrates. These substrates are generally inexpensive materials and provide benefits to the final article such as, for example, flexibility, conformability, specific surface properties, and ease of recycling. The inventive method may be performed at low cost since it requires a minimum number of process steps and materials, does not require extreme, specialized or slow process steps, and minimizes process waste and pollution.
The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims.